[Improve] Add clientFoundRows capabilities(config、commands、validate)

[wenyh1]

Add the capClientFoundRows configuration entry, add the manager command for capClientFoundRows, and validate capClientFoundRows on client login.

1、configure in bootstrap.cnf add：-DcapClientFoundRows=true
2、add commands on the manager, following：
show @@cap_client_found_rows;
enable @@cap_client_found_rows;
disable @@cap_client_found_rows;
3.、when the client is logged in, added validation of whether the client is consistent with the ClientFoundRows functionality on the dble